FEMALE BENEFIT, MALE RISK - POLYANDRY IN THE TRUE ARMYWORM PSEUDALETIA-UNIPUNCTA

In Lepidoptera polyandry is common and females may increase their life time reproductive output through repeated matings if they acquire esse ntial resources from male ejaculates. However, the paternity of males mating with previously-mated females is far from assured unless sperm precedence is absolute. In this study on the polyandrous armyworm, Pse udaletia unipuncta, we used two strains of male (the black-eyed wild t ype and a red-eyed homozygous, recessive mutant), mated with red-eyed females, to determine (i) whether male investment has any impact on fe male reproductive output, and (ii) if females do benefit from multiple matings, to what extent males fertilize the eggs to which they contri buted. Multiple mating resulted in a significant increase in both the fecundity and longevity of females. However, the degree of sperm prece dence (those eggs fertilized by the second male) varied from 0-100%, b ut was not affected by either male size or age, or by the duration of copulation. In cases where sperm precedence was <50% (xBAR = 12%) fema les produced significantly more eggs (1384 versus 940) prior to the se cond mating than females where sperm precedence was >50% (xBAR = 89%), indicating that the quality of the first mating influenced the fertil ization success of the female's second mate.